The county commissioners of such counties and the corporate authorities of such cities are authorized and empowered to enter into a joint contract or contracts, agreement or agreements, for the construction of such building or buildings and for the payment by each of them of the proportionate share of the cost of the construction, maintenance, and operation of such building or buildings, and for the use thereof, and in the case of public auditoriums for the rental to be charged thereof, and for the disposition for city and county purposes of any annual balance accruing from any rental derived from the use of such public auditorium.
53 P.S. § 1343